Teulon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Teulon clear sky chart from 2005-11-06 to 2024-03-23.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	12% 9% 4 8% 7% 4 5% 5% 6% 7% 34%	78153
	Night	10% 10% 5% 8% 7% 4 6% 5% 6% 7% 33%	81727
Transparency	Day	47% 8% 15% 21% 8% 1	77856
	Night	49% 8% 14% 20% 8% 1	81605
Seeing	Day	13% 9% 30% 29% 15% 4	15277
	Night	14% 7% 30% 33% 14% 2	25450

By Month

Percentage Cloud Cover NW (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	9% 13% 7% 9% 10% 6% 8% 6% 6% 5% 20%	2219
	11th to 20th	Day	5% 10% 6% 17% 15% 7% 8% 6% 6% 8% 11%	2199
	21st to end	Day	8% 17% 7% 13% 9% 5% 7% 5% 5% 7% 17%	2762
February	1st to 10th	Day	10% 11% 5% 10% 11% 6% 9% 7% 7% 6% 19%	1605
	11th to 20th	Day	7% 9% 4 9% 7% 5% 8% 7% 7% 10% 26%	1664
	21st to end	Day	6% 12% 5% 10% 8% 5% 7% 7% 6% 7% 27%	1484
March	1st to 10th	Day	12% 11% 5% 11% 9% 3 7% 6% 6% 6% 24%	1937
	11th to 20th	Day	8% 10% 5% 12% 9% 5% 6% 5% 5% 7% 28%	2088
	21st to end	Day	10% 10% 5% 9% 7% 4 5% 5% 5% 7% 32%	2200
April	1st to 10th	Day	10% 10% 4 7% 7% 3 5% 5% 5% 7% 38%	2204
	11th to 20th	Day	12% 9% 4 7% 6% 4 5% 5% 5% 6% 36%	2312
	21st to end	Day	13% 7% 3 6% 6% 4 6% 5% 6% 7% 36%	2340
May	1st to 10th	Day	17% 8% 3 6% 5% 3 4 4 4 6% 39%	2426
	11th to 20th	Day	17% 7% 3 6% 6% 3 5% 4 5% 7% 38%	2627
	21st to end	Day	20% 6% 3 5% 5% 3 5% 5% 4 7% 37%	2918
June	1st to 10th	Day	15% 7% 3 6% 5% 3 6% 5% 6% 8% 36%	2700
	11th to 20th	Day	15% 6% 3 5% 6% 4 6% 6% 6% 7% 36%	2700
	21st to end	Day	12% 6% 2 6% 6% 4 5% 6% 7% 9% 36%	2700
July	1st to 10th	Day	8% 4 2 4 4 3 6% 6% 7% 10% 47%	2700
	11th to 20th	Day	11% 4 2 4 5% 2 5% 5% 7% 9% 44%	2700
	21st to end	Day	8% 4 2 5% 5% 3 5% 5% 6% 9% 49%	2931
August	1st to 10th	Day	7% 5% 3 5% 5% 4 5% 5% 7% 8% 47%	2447
	11th to 20th	Day	10% 5% 2 5% 5% 3 5% 5% 5% 9% 46%	2301
	21st to end	Day	13% 5% 2 6% 5% 3 4 4 5% 7% 47%	2574
September	1st to 10th	Day	11% 5% 2 5% 4 3 3 5% 5% 8% 49%	2243
	11th to 20th	Day	13% 8% 3 8% 6% 3 5% 4 6% 8% 38%	1980
	21st to end	Day	16% 6% 3 6% 5% 3 4 5% 6% 8% 40%	1980
October	1st to 10th	Day	18% 9% 3 8% 5% 4 4 4 4 7% 33%	1836
	11th to 20th	Day	12% 13% 4 7% 7% 4 4 5% 6% 7% 31%	1751
	21st to end	Day	14% 14% 4 9% 8% 4 5% 6% 6% 6% 24%	1782
November	1st to 10th	Day	17% 13% 5% 9% 7% 4 5% 4 4 5% 26%	1501
	11th to 20th	Day	8% 15% 6% 11% 8% 3 6% 5% 5% 8% 25%	1520
	21st to end	Day	14% 13% 6% 10% 8% 4 5% 4 4 7% 25%	1371
December	1st to 10th	Day	9% 13% 7% 14% 11% 5% 6% 6% 6% 7% 17%	1330
	11th to 20th	Day	10% 13% 7% 13% 9% 4 6% 6% 6% 6% 21%	1679
	21st to end	Day	10% 10% 5% 9% 8% 4 6% 6% 6% 7% 29%	2442
January	1st to 10th	Night	5% 13% 7% 11% 8% 7% 9% 7% 6% 7% 21%	4737
	11th to 20th	Night	5% 13% 6% 13% 14% 8% 9% 6% 5% 5% 14%	4709
	21st to end	Night	8% 15% 8% 14% 8% 4 6% 5% 6% 5% 20%	4905
February	1st to 10th	Night	9% 12% 4 11% 8% 4 7% 6% 6% 7% 26%	2575
	11th to 20th	Night	7% 9% 3 8% 7% 4 7% 7% 6% 7% 34%	2403
	21st to end	Night	6% 10% 5% 8% 8% 4 6% 6% 6% 7% 34%	1987
March	1st to 10th	Night	9% 11% 5% 9% 7% 4 5% 5% 5% 7% 32%	2242
	11th to 20th	Night	7% 8% 4 6% 6% 3 4 5% 5% 8% 42%	2090
	21st to end	Night	12% 10% 5% 6% 6% 3 5% 5% 6% 8% 35%	2200
April	1st to 10th	Night	11% 6% 3 5% 6% 3 5% 6% 6% 8% 41%	1752
	11th to 20th	Night	13% 9% 4 7% 6% 3 4 6% 5% 7% 36%	1599
	21st to end	Night	11% 8% 3 6% 7% 3 6% 5% 5% 7% 39%	1620
May	1st to 10th	Night	16% 9% 4 5% 5% 3 5% 5% 6% 7% 37%	1533
	11th to 20th	Night	16% 5% 2 5% 5% 4 4 4 5% 8% 42%	1265
	21st to end	Night	17% 5% 2 6% 5% 3 4 4 6% 6% 43%	1358
June	1st to 10th	Night	12% 7% 3 5% 5% 4 4 5% 6% 10% 40%	1260
	11th to 20th	Night	14% 5% 2 4 6% 3 5% 5% 6% 8% 42%	1260
	21st to end	Night	8% 5% 2 6% 5% 3 4 5% 8% 10% 43%	1260
July	1st to 10th	Night	6% 3 2 3 3 2 4 5% 4 9% 59%	1260
	11th to 20th	Night	6% 3 2 4 4 3 5% 5% 7% 9% 52%	1260
	21st to end	Night	7% 4 2 4 4 3 4 5% 6% 10% 53%	1386
August	1st to 10th	Night	6% 3 1 4 4 3 4 4 5% 8% 56%	1491
	11th to 20th	Night	7% 4 1 3 5% 3 4 5% 6% 9% 54%	1600
	21st to end	Night	10% 6% 2 4 4 3 3 5% 5% 7% 51%	1782
September	1st to 10th	Night	9% 5% 2 6% 4 3 4 4 5% 7% 51%	1712
	11th to 20th	Night	12% 5% 2 5% 5% 2 5% 4 6% 8% 45%	1980
	21st to end	Night	16% 6% 2 6% 5% 3 3 4 5% 8% 42%	1980
October	1st to 10th	Night	17% 9% 3 6% 5% 3 5% 4 4 7% 37%	2106
	11th to 20th	Night	15% 10% 3 6% 6% 4 5% 6% 6% 6% 33%	2206
	21st to end	Night	14% 11% 5% 7% 7% 3 5% 5% 5% 6% 31%	2574
November	1st to 10th	Night	13% 12% 5% 8% 7% 3 6% 5% 6% 6% 28%	2575
	11th to 20th	Night	10% 14% 7% 10% 8% 4 5% 5% 5% 6% 27%	2660
	21st to end	Night	12% 13% 6% 12% 8% 4 6% 5% 5% 6% 25%	2807
December	1st to 10th	Night	6% 11% 7% 11% 12% 5% 6% 6% 6% 8% 22%	2850
	11th to 20th	Night	8% 14% 8% 11% 7% 4 6% 6% 5% 7% 24%	3518
	21st to end	Night	8% 10% 5% 10% 9% 5% 6% 5% 6% 7% 28%	5225

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	64% 6% 14% 14% 3	2219
	11th to 20th	Day	69% 5% 11% 12% 3	2220
	21st to end	Day	65% 7% 10% 13% 5%	2762
February	1st to 10th	Day	61% 7% 12% 11% 8% 1	1605
	11th to 20th	Day	50% 8% 14% 20% 7%	1673
	21st to end	Day	53% 8% 12% 18% 8%	1484
March	1st to 10th	Day	58% 7% 12% 15% 7%	1937
	11th to 20th	Day	53% 9% 12% 19% 6%	2090
	21st to end	Day	50% 7% 15% 19% 8% 1	2200
April	1st to 10th	Day	46% 7% 13% 24% 10% 1	2204
	11th to 20th	Day	46% 7% 11% 21% 13% 2	2312
	21st to end	Day	45% 8% 16% 23% 7% 2	2340
May	1st to 10th	Day	45% 6% 14% 23% 12% 1	2426
	11th to 20th	Day	46% 5% 11% 23% 13% 1	2631
	21st to end	Day	46% 8% 12% 20% 13% 1	2918
June	1st to 10th	Day	44% 8% 15% 22% 10% 1	2700
	11th to 20th	Day	44% 9% 15% 20% 11% 1	2700
	21st to end	Day	42% 11% 18% 22% 7%	2700
July	1st to 10th	Day	29% 9% 21% 29% 11%	2626
	11th to 20th	Day	32% 10% 18% 29% 10% 1	2619
	21st to end	Day	31% 10% 19% 29% 10%	2768
August	1st to 10th	Day	32% 9% 21% 29% 8%	2431
	11th to 20th	Day	34% 9% 22% 29% 6%	2301
	21st to end	Day	36% 8% 17% 30% 8%	2574
September	1st to 10th	Day	33% 8% 18% 32% 8% 1	2243
	11th to 20th	Day	44% 9% 18% 25% 4	1980
	21st to end	Day	42% 7% 18% 28% 6%	1980
October	1st to 10th	Day	52% 7% 16% 20% 5%	1836
	11th to 20th	Day	51% 9% 13% 22% 4 1	1751
	21st to end	Day	58% 10% 16% 13% 3	1782
November	1st to 10th	Day	58% 9% 13% 16% 4 1	1501
	11th to 20th	Day	57% 11% 14% 14% 4	1520
	21st to end	Day	60% 6% 18% 13% 3	1371
December	1st to 10th	Day	64% 10% 13% 10% 3	1330
	11th to 20th	Day	61% 8% 15% 12% 4	1680
	21st to end	Day	53% 8% 13% 18% 8%	2442
January	1st to 10th	Night	59% 9% 13% 15% 5%	4737
	11th to 20th	Night	70% 7% 8% 13% 3	4750
	21st to end	Night	64% 6% 11% 14% 4	4905
February	1st to 10th	Night	56% 7% 12% 15% 9%	2575
	11th to 20th	Night	45% 8% 16% 21% 9%	2404
	21st to end	Night	48% 8% 12% 22% 10%	1987
March	1st to 10th	Night	51% 7% 12% 21% 9% 1	2242
	11th to 20th	Night	39% 7% 14% 27% 11% 1	2090
	21st to end	Night	47% 8% 13% 20% 11% 2	2200
April	1st to 10th	Night	40% 5% 13% 23% 17% 3	1752
	11th to 20th	Night	46% 5% 10% 20% 16% 3	1599
	21st to end	Night	44% 7% 13% 23% 11% 2	1620
May	1st to 10th	Night	44% 6% 12% 24% 13%	1533
	11th to 20th	Night	40% 6% 13% 25% 13% 3	1265
	21st to end	Night	41% 7% 12% 21% 16% 2	1358
June	1st to 10th	Night	40% 9% 17% 22% 12% 1	1260
	11th to 20th	Night	39% 8% 17% 20% 14% 2	1260
	21st to end	Night	33% 9% 26% 24% 8% 1	1260
July	1st to 10th	Night	22% 9% 18% 37% 14% 1	1225
	11th to 20th	Night	27% 9% 20% 29% 12% 2	1218
	21st to end	Night	27% 6% 16% 38% 12% 1	1309
August	1st to 10th	Night	26% 8% 19% 34% 12% 1	1483
	11th to 20th	Night	26% 8% 23% 31% 11% 1	1600
	21st to end	Night	31% 7% 14% 34% 13% 1	1782
September	1st to 10th	Night	33% 7% 17% 31% 13% 1	1712
	11th to 20th	Night	37% 8% 19% 26% 10% 1	1980
	21st to end	Night	42% 6% 17% 27% 8%	1980
October	1st to 10th	Night	47% 9% 15% 22% 7%	2106
	11th to 20th	Night	49% 8% 15% 23% 6%	2206
	21st to end	Night	52% 9% 16% 19% 4	2574
November	1st to 10th	Night	55% 8% 15% 15% 5% 1	2575
	11th to 20th	Night	59% 9% 14% 13% 5%	2660
	21st to end	Night	62% 7% 14% 13% 4	2807
December	1st to 10th	Night	59% 8% 17% 12% 4	2850
	11th to 20th	Night	58% 8% 15% 13% 6%	3516
	21st to end	Night	53% 8% 12% 16% 10% 1	5225

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	10% 7% 33% 32% 14% 4	270
	11th to 20th	Day	10% 7% 32% 34% 16% 2	270
	21st to end	Day	16% 6% 28% 30% 15% 5%	297
February	1st to 10th	Day	12% 6% 33% 37% 8% 3	270
	11th to 20th	Day	10% 11% 31% 28% 14% 5%	270
	21st to end	Day	6% 9% 37% 31% 16% 1	225
March	1st to 10th	Day	15% 8% 30% 31% 15% 1	270
	11th to 20th	Day	10% 8% 36% 28% 15% 3	270
	21st to end	Day	13% 6% 33% 30% 15% 3	270
April	1st to 10th	Day	13% 8% 35% 33% 9% 3	464
	11th to 20th	Day	15% 11% 29% 30% 12% 2	590
	21st to end	Day	14% 10% 36% 26% 12% 2	600
May	1st to 10th	Day	15% 12% 31% 30% 10% 2	603
	11th to 20th	Day	19% 10% 25% 26% 17% 4	625
	21st to end	Day	20% 10% 23% 27% 17% 3	679
June	1st to 10th	Day	15% 11% 29% 24% 14% 7%	630
	11th to 20th	Day	16% 11% 30% 28% 11% 4	630
	21st to end	Day	11% 7% 25% 32% 20% 6%	630
July	1st to 10th	Day	9% 6% 30% 30% 19% 7%	621
	11th to 20th	Day	13% 8% 26% 31% 16% 6%	618
	21st to end	Day	6% 5% 29% 31% 20% 9%	684
August	1st to 10th	Day	8% 5% 28% 31% 20% 8%	626
	11th to 20th	Day	10% 6% 23% 31% 21% 8%	615
	21st to end	Day	12% 7% 27% 30% 20% 4	693
September	1st to 10th	Day	10% 9% 32% 33% 14% 3	533
	11th to 20th	Day	16% 10% 36% 26% 10% 3	270
	21st to end	Day	22% 5% 32% 31% 10% 1	270
October	1st to 10th	Day	21% 10% 26% 29% 10% 4	270
	11th to 20th	Day	13% 14% 32% 27% 12% 2	270
	21st to end	Day	23% 11% 31% 22% 12% 2	297
November	1st to 10th	Day	25% 11% 24% 30% 9% 1	270
	11th to 20th	Day	14% 11% 37% 27% 10% 1	270
	21st to end	Day	17% 14% 37% 27% 5%	270
December	1st to 10th	Day	13% 8% 36% 25% 16% 3	270
	11th to 20th	Day	13% 8% 39% 30% 9% 1	270
	21st to end	Day	11% 8% 30% 30% 16% 5%	297
January	1st to 10th	Night	11% 7% 36% 31% 13% 2	950
	11th to 20th	Night	14% 7% 32% 34% 11% 1	950
	21st to end	Night	15% 6% 31% 34% 13% 1	1045
February	1st to 10th	Night	14% 6% 27% 37% 15% 1	950
	11th to 20th	Night	11% 6% 30% 35% 15% 3	929
	21st to end	Night	10% 6% 35% 30% 17% 2	731
March	1st to 10th	Night	14% 6% 30% 30% 16% 2	722
	11th to 20th	Night	10% 6% 42% 29% 12% 2	570
	21st to end	Night	17% 5% 29% 32% 14% 4	600
April	1st to 10th	Night	14% 6% 31% 36% 11% 2	540
	11th to 20th	Night	17% 5% 27% 35% 14% 1	533
	21st to end	Night	15% 7% 32% 34% 11% 1	540
May	1st to 10th	Night	19% 8% 28% 35% 10% 1	540
	11th to 20th	Night	16% 7% 31% 30% 15% 1	531
	21st to end	Night	18% 7% 28% 33% 13% 1	584
June	1st to 10th	Night	16% 5% 29% 31% 19% 1	540
	11th to 20th	Night	14% 6% 28% 36% 14% 1	540
	21st to end	Night	10% 5% 22% 40% 21% 1	540
July	1st to 10th	Night	7% 4 24% 43% 21% 1	525
	11th to 20th	Night	7% 4 26% 41% 20% 2	522
	21st to end	Night	8% 3 20% 41% 25% 3	591
August	1st to 10th	Night	8% 3 19% 48% 20% 2	537
	11th to 20th	Night	8% 4 22% 40% 22% 4	534
	21st to end	Night	12% 5% 21% 40% 20% 2	594
September	1st to 10th	Night	10% 5% 30% 34% 19% 2	540
	11th to 20th	Night	15% 6% 25% 40% 14%	540
	21st to end	Night	17% 5% 33% 33% 12% 1	540
October	1st to 10th	Night	21% 6% 32% 32% 9%	666
	11th to 20th	Night	19% 7% 31% 30% 12% 1	766
	21st to end	Night	20% 9% 29% 30% 10% 1	990
November	1st to 10th	Night	19% 8% 35% 26% 11% 1	925
	11th to 20th	Night	16% 9% 36% 26% 9% 3	950
	21st to end	Night	18% 10% 40% 26% 7% 1	950
December	1st to 10th	Night	11% 8% 31% 36% 13% 2	950
	11th to 20th	Night	15% 9% 36% 30% 9% 1	950
	21st to end	Night	18% 7% 30% 30% 13% 2	1045

Page generated at 2024-03-19 22:31:03. Version ac07

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